System Messages

Declared in:  be/app/AppDefs.h
more...

B_MOUSE_WHEEL_CHANGED

Source: The system.
Target: The BWindow of the view the mouse is pointing to, and that of any other view that sets B_POINTER_EVENTS in its event mask (see BView::SetEventMask())
Hook: none

B_MOUSE_WHEEL_CHANGED is sent when the mouse wheel is distrubed. The message contains these fields:

Field	Type code	Description
"when"	B_INT64_TYPE	Event time, in microseconds since 01/01/70
"be:wheel_delta_x"	B_FLOAT_TYPE	The change in the wheel's horizontal position as a value between -1.0 (left) and 1.0 (right).
"be:wheel_delta_x"	B_FLOAT_TYPE	The change in the wheel's vertical position as a value between -1.0 (down) and 1.0 (up).

B_OBSERVER_NOTICE_CHANGE

Source: BHandler::SendNotices()
Target: Other BHandlers that are watching the notice-sender
Hook: none

B_OBSERVER_NOTICE_CHANGE is sent when the source object (a BHandler) invokes SendNotices(), which broadcasts a notice to all of its "watchers" (other BHandlers). A BHandler can register to be a watcher by calling BHandler::StartWatching().

Field	Type code	Description
B_OBSERVE_WHICH_CHANGE	B_INT32_TYPE	The change that caused the notification to be sent, as taken from an argument to SendNotices().
"be:old_what"	B_INT32_TYPE	The what field from the BMessage that's passed to SendNotices().
Other fields	...	The rest of the fields are copied from the message that's passed to SendNotices().

Source: A BChannelControl object
Target: Set through SetTarget() et al.
Hook: none

An n-channeled BChannelControl adds the following field to the BControl-defined value-changed message that it sends to its target.

Field	Type code	Description
"be:channel_value" [n]	B_INT32_TYPE	The value of each of the object's channels.

This field usurps (but doesn't remove) the "be:value" field that's added by BControl.